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Chapter 35

Chapter 35. Section 1 Molluska. Characteristics of Mollusks. Some are filter-feeders while others are fast-moving predators with complex nervous systems Coelomates - true body cavity. Characteristics of Mollusks. Aquatic mollusks have a larval stage of development called a trochophore

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Chapter 35

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  1. Chapter 35 Section 1 Molluska

  2. Characteristics of Mollusks • Some are filter-feeders while others are fast-moving predators with complex nervous systems • Coelomates- true body cavity

  3. Characteristics of Mollusks • Aquatic mollusks have a larval stage of development called a trochophore • Trochophores are motile and disperse throughout bodies of water

  4. Body Plan of Mollusks • 2 main regions- head-foot & visceral mass • Head-foot- consists of the head, mouth, sensory structures, and foot- large muscular organ usually used for locomotion

  5. Body Plan of Mollusks • Visceral mass- (located above the head-foot) contains the heart, organs of digestion, excretion, & reproduction • Visceral mass is covered by a layer of epidermis called the mantle

  6. Body Plan of Mollusks • Most mollusks- mantle secretes hard shells containing calcium carbonate • Why have a shell???

  7. Body Plan of Mollusks • Mantle cavity- space between the mantle and visceral mass • Gills are protected by mantle cavity

  8. Body Plan of Mollusks • Ganglia- more complex nervous system that controls locomotion, feeding, and sensory information (light, touch, etc)

  9. Body Plan of Mollusks • Radula- main feeding adaptation • Tongue-like strip of tissue covered with tough, abrasive teeth that point backwards • Terrestrial snails- cut through leaves • Aquatic snails- scrape algae

  10. Class Gastropoda • Gastropods • snails, conchs • slugs & nudibranchs

  11. Snail

  12. Conch

  13. Slug

  14. Nudibranch

  15. Class Bivalvia • Bivalves- two shells connected by a hinge • Closes its shell with adductor muscles, when the muscles relax, the valves open • Most bivalves are sessile

  16. Class Bivalvia • Clams • Bury in sand or mud • Feeding: Cilia beats on the gills and set up a current of water that enters through the incurrent siphon and leaves though the excurrent siphon

  17. Clam

  18. Class Cephalopoda • Cephalopod- “head foot” • Free-swimming & have tentacles • Nervous system is advanced- cephalopod brain is largest invertebrate brain • Ex: Octopi can perform tasks & distinguish between objects

  19. Class Cephalopoda • Release dark fluid to distract predators • Chromatophores- pigment cells that allow the organism to change colors quickly

  20. Squid • Move by pumping in water though their siphons • Largest invertebrate- Architeuthis- 60 feet long and up to 2,000 lbs!

  21. Octopus

  22. REVIEW!!! • What purpose does a radula have? • Describe the characteristics of mollusks. • Name the three major classes of mollusks & an example of each.

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